An engine employing a direct-injection fuel system may typically inject one or more fuel jets, such as diesel fuel jets, into a combustion chamber of the engine. Each of the fuel jets may contact air present in the combustion chamber and may ignite into a flame during a combustion process. In many situations, the fuel jet may burn inefficiently and/or incompletely due to various factors, such as limited entrainment or mixing of air with the fuel jet, limited turbulence within the combustion chamber, limited flame combustion rate and/or soot oxidation, limited flame speed, and so on. In such a situation, the incomplete combustion and/or incomplete mixing of the fuel jet with the air may result in increased soot formation, increased emission, reduced fuel efficiency, higher equivalence ratio, increased service intervals, increased maintenance cost, and so on. Hence, there is a need for an improved fuel injection system.
U.S. Pat. No. 3,132,633 describes a piston assembly for an internal combustion engine having a fuel injection system and an injector nozzle. The assembly includes a piston head reciprocable in the engine and includes a spherical indentation in an upper surface thereof. The assembly also includes an insert secured in the indentation and includes a convex surface adjacent to the indentation to form a bowl-shaped pre-combustion chamber. The insert includes a central opening provided therein, aligned with the injector nozzle, and in communication with the pre-combustion chamber to provide a combustible mixture thereto for partial combustion therein. The insert also includes a plurality of orifices radially spaced from the central opening and in communication between the pre-combustion chamber and the upper surface of the piston head to provide the combustible mixture from the pre-combustion chamber.